I am worried about .............................. he is safe. A.if B.whether C.Either could be used here Answer and Feedback Answer:B Feedback:We cannot use 'if' after a preposition. We use 'whether' instead. do you want? view more test Xem thêm Share this post Some other questions you may be interested in. Which is the mathematical property used in this addition equation: (57 + 63) + 14 = 57 + (63 + 14)? What is the name of the property used in this addition equation: 12 + 0 = 12? What is the greatest common factor (GCF) of 24 and 36? What is the least common multiple (LCM) of 5, 6, and 10? What kind of fractions are 4/4, 9/8, and 7/4? Which of these are considered the two developers of the modern calculus? What are the two basic processes in calculus? When we find the extrema of a function we use this. Which statement is not true about functions? When you study calculus, you usually also study this branch of geometry.